// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package ethapi
import (
"encoding/json"
"errors"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/robertkrimen/otto"
)
// fakeBig is used to provide an interface to Javascript for 'big.NewInt'
type fakeBig struct{}
// NewInt creates a new big.Int with the specified int64 value.
func (fb *fakeBig) NewInt(x int64) *big.Int {
return big.NewInt(x)
}
// OpCodeWrapper provides a JavaScript-friendly wrapper around OpCode, to convince Otto to treat it
// as an object, instead of a number.
type opCodeWrapper struct {
op vm.OpCode
}
// toNumber returns the ID of this opcode as an integer
func (ocw *opCodeWrapper) toNumber() int {
return int(ocw.op)
}
// toString returns the string representation of the opcode
func (ocw *opCodeWrapper) toString() string {
return ocw.op.String()
}
// isPush returns true if the op is a Push
func (ocw *opCodeWrapper) isPush() bool {
return ocw.op.IsPush()
}
// MarshalJSON serializes the opcode as JSON
func (ocw *opCodeWrapper) MarshalJSON() ([]byte, error) {
return json.Marshal(ocw.op.String())
}
// toValue returns an otto.Value for the opCodeWrapper
func (ocw *opCodeWrapper) toValue(vm *otto.Otto) otto.Value {
value, _ := vm.ToValue(ocw)
obj := value.Object()
obj.Set("toNumber", ocw.toNumber)
obj.Set("toString", ocw.toString)
obj.Set("isPush", ocw.isPush)
return value
}
// memoryWrapper provides a JS wrapper around vm.Memory
type memoryWrapper struct {
memory *vm.Memory
}
// slice returns the requested range of memory as a byte slice
func (mw *memoryWrapper) slice(begin, end int64) []byte {
return mw.memory.Get(begin, end-begin)
}
// getUint returns the 32 bytes at the specified address interpreted
// as an unsigned integer
func (mw *memoryWrapper) getUint(addr int64) *big.Int {
ret := big.NewInt(0)
ret.SetBytes(mw.memory.GetPtr(addr, 32))
return ret
}
// toValue returns an otto.Value for the memoryWrapper
func (mw *memoryWrapper) toValue(vm *otto.Otto) otto.Value {
value, _ := vm.ToValue(mw)
obj := value.Object()
obj.Set("slice", mw.slice)
obj.Set("getUint", mw.getUint)
return value
}
// stackWrapper provides a JS wrapper around vm.Stack
type stackWrapper struct {
stack *vm.Stack
}
// peek returns the nth-from-the-top element of the stack.
func (sw *stackWrapper) peek(idx int) *big.Int {
return sw.stack.Data()[len(sw.stack.Data())-idx-1]
}
// length returns the length of the stack
func (sw *stackWrapper) length() int {
return len(sw.stack.Data())
}
// toValue returns an otto.Value for the stackWrapper
func (sw *stackWrapper) toValue(vm *otto.Otto) otto.Value {
value, _ := vm.ToValue(sw)
obj := value.Object()
obj.Set("peek", sw.peek)
obj.Set("length", sw.length)
return value
}
// dbWrapper provides a JS wrapper around vm.Database
type dbWrapper struct {
db vm.StateDB
}
// getBalance retrieves an account's balance
func (dw *dbWrapper) getBalance(addr common.Address) *big.Int {
return dw.db.GetBalance(addr)
}
// getNonce retrieves an account's nonce
func (dw *dbWrapper) getNonce(addr common.Address) uint64 {
return dw.db.GetNonce(addr)
}
// getCode retrieves an account's code
func (dw *dbWrapper) getCode(addr common.Address) []byte {
return dw.db.GetCode(addr)
}
// getState retrieves an account's state data for the given hash
func (dw *dbWrapper) getState(addr common.Address, hash common.Hash) common.Hash {
return dw.db.GetState(addr, hash)
}
// exists returns true iff the account exists
func (dw *dbWrapper) exists(addr common.Address) bool {
return dw.db.Exist(addr)
}
// toValue returns an otto.Value for the dbWrapper
func (dw *dbWrapper) toValue(vm *otto.Otto) otto.Value {
value, _ := vm.ToValue(dw)
obj := value.Object()
obj.Set("getBalance", dw.getBalance)
obj.Set("getNonce", dw.getNonce)
obj.Set("getCode", dw.getCode)
obj.Set("getState", dw.getState)
obj.Set("exists", dw.exists)
return value
}
// JavascriptTracer provides an implementation of Tracer that evaluates a
// Javascript function for each VM execution step.
type JavascriptTracer struct {
vm *otto.Otto // Javascript VM instance
traceobj *otto.Object // User-supplied object to call
log map[string]interface{} // (Reusable) map for the `log` arg to `step`
logvalue otto.Value // JS view of `log`
memory *memoryWrapper // Wrapper around the VM memory
memvalue otto.Value // JS view of `memory`
stack *stackWrapper // Wrapper around the VM stack
stackvalue otto.Value // JS view of `stack`
db *dbWrapper // Wrapper around the VM environment
dbvalue otto.Value // JS view of `db`
err error // Error, if one has occurred
}
// NewJavascriptTracer instantiates a new JavascriptTracer instance.
// code specifies a Javascript snippet, which must evaluate to an expression
// returning an object with 'step' and 'result' functions.
func NewJavascriptTracer(code string) (*JavascriptTracer, error) {
vm := otto.New()
vm.Interrupt = make(chan func(), 1)
// Set up builtins for this environment
vm.Set("big", &fakeBig{})
jstracer, err := vm.Object("(" + code + ")")
if err != nil {
return nil, err
}
// Check the required functions exist
step, err := jstracer.Get("step")
if err != nil {
return nil, err
}
if !step.IsFunction() {
return nil, fmt.Errorf("Trace object must expose a function step()")
}
result, err := jstracer.Get("result")
if err != nil {
return nil, err
}
if !result.IsFunction() {
return nil, fmt.Errorf("Trace object must expose a function result()")
}
// Create the persistent log object
log := make(map[string]interface{})
logvalue, _ := vm.ToValue(log)
// Create persistent wrappers for memory and stack
mem := &memoryWrapper{}
stack := &stackWrapper{}
db := &dbWrapper{}
return &JavascriptTracer{
vm: vm,
traceobj: jstracer,
log: log,
logvalue: logvalue,
memory: mem,
memvalue: mem.toValue(vm),
stack: stack,
stackvalue: stack.toValue(vm),
db: db,
dbvalue: db.toValue(vm),
err: nil,
}, nil
}
// Stop terminates execution of any JavaScript
func (jst *JavascriptTracer) Stop(err error) {
jst.vm.Interrupt <- func() {
panic(err)
}
}
// callSafely executes a method on a JS object, catching any panics and
// returning them as error objects.
func (jst *JavascriptTracer) callSafely(method string, argumentList ...interface{}) (ret interface{}, err error) {
defer func() {
if caught := recover(); caught != nil {
switch caught := caught.(type) {
case error:
err = caught
case string:
err = errors.New(caught)
case fmt.Stringer:
err = errors.New(caught.String())
default:
panic(caught)
}
}
}()
value, err := jst.traceobj.Call(method, argumentList...)
ret, _ = value.Export()
return ret, err
}
func wrapError(context string, err error) error {
var message string
switch err := err.(type) {
case *otto.Error:
message = err.String()
default:
message = err.Error()
}
return fmt.Errorf("%v in server-side tracer function '%v'", message, context)
}
// CaptureState implements the Tracer interface to trace a single step of VM execution
func (jst *JavascriptTracer) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost *big.Int, memory *vm.Memory, stack *vm.Stack, contract *vm.Contract, depth int, err error) error {
if jst.err == nil {
jst.memory.memory = memory
jst.stack.stack = stack
jst.db.db = env.StateDB
ocw := &opCodeWrapper{op}
jst.log["pc"] = pc
jst.log["op"] = ocw.toValue(jst.vm)
jst.log["gas"] = gas.Int64()
jst.log["gasPrice"] = cost.Int64()
jst.log["memory"] = jst.memvalue
jst.log["stack"] = jst.stackvalue
jst.log["depth"] = depth
jst.log["account"] = contract.Address()
jst.log["err"] = err
_, err := jst.callSafely("step", jst.logvalue, jst.dbvalue)
if err != nil {
jst.err = wrapError("step", err)
}
}
return nil
}
// GetResult calls the Javascript 'result' function and returns its value, or any accumulated error
func (jst *JavascriptTracer) GetResult() (result interface{}, err error) {
if jst.err != nil {
return nil, jst.err
}
result, err = jst.callSafely("result")
if err != nil {
err = wrapError("result", err)
}
return
}
